The refinement of an equation based on clinical and pathologic features of women with estrogen receptor-positive breast cancer may eliminate the need for Oncotype DX (ODX) to identify patients who have high risk of disease recurrence, according to research that will be presented at the 2017 San Antonio Breast Cancer Symposium.

Oncotype DX is a clinically useful tool in determining the risk of cancer recurrence and potential benefit of receiving adjuvant chemotherapy among patients with breast cancer, but is associated with high cost.

For this study, researchers retrospectively evaluated the Oncotype DX scores and outcomes of 190 patients with early-stage breast cancer and divided them into training and validation sets.

Clinical and pathologic variables such as age, estrogen-receptor (ER) and progesterone-receptor (PR) status, tumor size (pT), Elston-Ellis grade, and Ki67, were analyzed by a multiple linear regression model to determine which variables are significantly associated with Oncotype DX scores. Significant variable coefficients were used to formulate an equation that predicts high risk and a threshold score was determined, which was then applied to the training set and verified in the validation set.

The linear predictor was (0.2544 × pT) – (0.0739 × PR) + (0.0861 × Ki67) + (5.4232 × Elston grade). For this equation, the authors determined a score of 14 was an appropriate threshold to differentiate high-risk patients from patients with low or intermediate risks, and the test accurately identified patients who were at high risk of recurrence with 78% sensitivity, 72% specificity, and 98% negative predictive value.

The authors concluded, “[t]he observed ODX distribution in our patients in similar to previously reported series suggesting that this equation could be informative in similar clinical settings. Additional external testing using new datasets is ongoing.”

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